1. Field of the Invention
The present invention relates generally to a trouble-shooting apparatus useful for tracing electrical conductors in cables or locating short circuits in such cables, and more particularly, to an apparatus designed to be connected in the fuse circuit or other convenient circuit point in the circuit to be tested and used with an ammeter probe of the clamp-on type to trace electrical conductors and locate short circuits by detecting a pulsating current generated by the test apparatus.
2. Description of the Prior Art
In the control systems and data processing industries especially and in all industries which produce or employ machines having electrical wiring which varies from the relatively simple to the complex, there exists the need to be able to quickly trouble-shoot the electrical circuitry of those machines both during the production and maintenance of the machines. Typical of the circuits which require quick and efficient troubleshooting are automotive circuits which are low voltage DC, control systems circuits which may be both low voltage AC and DC circuits, and power distribution circuits which may be either or both high voltage AC or DC circuits. For example, in the production of a large scale data processing machine, it is often necessary to trace electrical conductors in large and multiply branched cables. Moreover, when production equipment goes down as a result of a short circuit, expensive down time can be incurred by the user of that equipment.
In order to facilitate the tracing of an electrical conductor or the location of a short circuit, testing devices have been devised which supply a pulsating current to the circuit being tested. One example of such a device is disclosed in U.S. Pat. No. 3,623,142. This patent describes a cable locator including a cam-operated switch means for impressing a pulsing current on the conductor. A synchronous motor is used to drive a cam member which in turn operates a make and break switch to impress a pulsing current of known amplitude to the conductor which is then subsequently identified by a clamp-on ammeter. While the concept is good, the implementation as described in the patent has several disadvantages. First, it requires a separate power supply to supply the pulsating current thereby limiting its use to the availability of an AC receptacle. Second, it is not useable for both low voltage and high voltage circuits. Third, it cannot be readily applied to both AC and DC circuits of a wide range of voltages. This lack of versatility is a considerable drawback when troubleshooting a variety of electrical circuits. Moreover, adequate circuit protection has not been provided for the testing of a variety of circuits.
Another example of a short locating device known in the prior art is disclosed in U.S. Pat. No. 3,621,384. This patent discloses a means for locating an intermittent DC short circuit by placing a transducer in parallel with the fuse. A search coil is used to provide an audio indication via earphones or the like. This system, however, has several disadvantages. First, it will not function on both AC and DC circuits. Second, the polarity cannot be reversed. Third, this system requires a transducer unit and a searching unit both of which require complex electronic circuitry.